Elektronen- und Ionenleitung in elektrolytischen Deckschichten und ihre Bedeutung für die Passivität der Metalle

Abstract

The electrochemical behaviour of metal electrodes on which non-metallic surface layers may be deposited electrolytically is essentially governed by the properties of the substance forming the layer. Electrode surface layers of this kind can at tain a finite stationary thickness only if the steady loss suffered by the layer substance due to its solubility in the electrolytic solution is counterbalanced by an equivalent electrolytic formation process. If, in particular, the surface layer is free of pores, a certain transfer of matter and electric charge across the layer is necessary for the formation process. Therefore the semi-conductor properties of the layer substance are most essential. The problem of electrolytic surface layers is, in this respect, closely connected with the problems of semi-conductor physics.

In the first section is shown how, for non-conducting, ion conducting, and electron conducting layers, conclusions concerning the conduction mechanism acting in the respective layer which is formed may be arrived at from recorded voltage and current changes following the switching-on of the electrolytic current.

The second section deals with the migration of charge and matter through semiconducting electrolytic layers.

The third section discusses several representative interface phenomena caused by semi-conducting passivating layers.